Opportunities and challenges: Experimental and kinetic analysis of anaerobic co-digestion of food waste and rendering industry streams for biogas production

Large amounts of food waste and sewage sludge exert a hazardous environmental impact in several countries. Producing biogas and digestate from food and industrial waste is one of the solutions for waste management, stabilization of sludge, resource and energy recovery and reductions in the amount of waste. However, biogas production from such substrates has challenges in degradation efficiency, inhibitory effects and other challenges, and thus co-digestion and pretreatment techniques could be applied to enhance biogas production. The aim of this study is to explore the effects of co-digestion of food waste, meat and bone meal and rendering wastewater sludge. First, thermal pretreatment was performed (35°C, 5 days) by adding the rendering-industry streams to food waste in the amounts of 0, 5, 10 and 15% on a total solid basis, and further anaerobic digestion (40.5°C, ca. 40 days) was then performed. Both experimental and kinetic analysis were conducted, and the major factors regarding opportunities and challenges in the two-stage process are discussed. Results have shown that both co-substrates from rendering industry decreased the biogas yield of food waste. When 5% of them was added to food waste, meat and bone meal decreased biogas production by 12%, and wastewater sludge decreased it by 23%. Both co-substrates, on the other side, increased the rate of reaction of food waste digestion when applying different common kinetic models.